This renewal proposal for the USC Roybal Center for Financial Decision Making will continue and expand upon the work that we have already done to improve our understanding of how people reach decisions about issues affecting their economic status in old age. Building on earlier work, the renewal proposal focuses on the issue of complexity: which decisions are particularly challenging for individuals, which simplifications would improve decision making, and which interventions would be most helpful in improving the capability to make better decisions? We will pay attention to the costs of sub-optimal choices, distinguishing between cases in which suboptimal decisions in a complex environment may lead to large losses in welfare and cases in which complexity does not have substantial consequences. Simplifications of choice environments may reduce the likelihood of errors, but at the same time may also carry its own costs, if for example it requires reducing the set of options available. Our approach will be both conceptual (what is complexity; what dimensions matter most) and experimental. We will conduct a series of pilot projects aimed at understanding the effect of the choice architecture on decisions and understanding how the choice environment can be changed to improve decision-making. For the experimental part, we will rely heavily on the RAND-USC American Life Panel, but we also take advantage of natural experiments, and conduct cognitive interviews and focus groups where appropriate. We aim to translate the findings of the pilot projects into the development of decision tools as well as concrete recommendations for simplifications of choice architecture and language used to describe decisions people have to make.